In complex machines that have to operate over too long a period for the driving to be handled by a single operator, use is generally made of automatic driving devices and/or driving stations with two or more operators that can take over from one another to handle the driving of the machine.
When an operator is relieved of the driving, he or she benefits from a rest period but, in many cases, the operator remains at his or her driving station and simply places his or her seat in a position ensuring him or her of a position of optimal muscular and skeletal relaxation. In most cases, the back rest of the seat can be inclined to a greater or lesser degree backwards to obtain the rest position.
This situation is typical in the piloting of civilian airplanes in which two pilots handle the driving of the airplane either simultaneously in a co-ordinated manner in the critical flight phases (take-off and landing in particular) or, alternatively, in the flight phases in which the workload is reduced (cruising for example).
However, when the pilot in the rest phase uses a relatively inclined position of his or her seat to stretch out, he or she no longer has, in the natural position that he or she has adopted, the information displayed on the control instruments and he or she leaves the piloting loop. In case of emergency, additional time is then needed for him or her to take in the information and understand the situation in which he or she has to intervene.
Because of this, it is commonplace for pilots, in the rest period, not to place their seats in an optimal position for resting and to prefer, to the detriment of their physical recovery through a real rest period, to remain in a working position in order to remain informed of the flight parameters and be able to more effectively resume a flight or machine driving activity.